Roller skates in current use which accommodate turning have two basic designs commonly termed "conventional" and "roller blade". Conventional skates have four flat wheels mounted on an external boot plate for each skate and get their turning action when the plate and boot are leaned to one side or the other. The whhels and truck remain horizontal to the skating surface but rotate slightly turning the skate in the direction of leaning. The trucks mount to the plate with a bolt having rubber cushions on one end of the truck and a free moving pivot at the other end.
Roller blade skates are designed somewhat similar to ice skates using relatively narrow rounded wheels in longitudinal alignment having an arcuate contact profile extending to the lowest point at the middle. The skate can lean on any one of the wheels while the plate and truck remain in line because of the rounded sides of the wheels. The skate gets its turning action with limited rocking back and forth while leaning in a manner similar to an ice skate. Roller blades normally have five wheels in line per skate that mount directly to the plate with no turning or leaning movements.